The value of searching films without specific preconceptions.

The detection of simulated pulmonary nodules was measured in three different situations that required: (1) reports of all significant chest findings (Free Search), (2) only reports of possible nodules (Nodule Search), or (3) evaluation of particular film locations as nodules (Specified Location). ROC curves from these conditions compared how accurately readers could distinguish between the nodule and normal "test locations," and between the films that did and did not contain nodules. In replication of previous results for heterogeneous chest findings, detection accuracy was superior when readers had to search the films. Each reader's distinctions between the nodule and normal test locations became considerably less accurate when these locations were prespecified for explicit evaluation. When asked to search only for pulmonary nodules, most readers substantially increased their false reports of nodules at each level of confidence, with little improvement in their (already high) true-detection rates. Searching for nodules increased both the true-detection and false-detection rates for two readers, who simply appeared to relax a strong bias against reporting nodules in the initial Free-Search situation.